1. Field of the Invention
The present invention relates to an exposure apparatus, an exposure method and a device manufacturing method employing the exposure method, for use in the manufacture of semiconductor devices, liquid-crystal devices, etc. More particularly, the present invention relates to an exposure apparatus, an exposure method and a device manufacturing method employing the exposure method, for accurately aligning an original mask, such as a reticle, with a substrate, such as a semiconductor wafer or glass substrate, to achieve good exposure performance.
2. Description of the Related Art
As the miniaturization and degree of integration are currently promoted in the design of semiconductor integrated circuits, such as LSIs (Large-Scale Integrated Circuits), alignment accuracy requirements in integrated circuits have become rigorous. Semiconductor device manufacturing exposure apparatuses employ methods called a step-and-repeat method and a step-and-scan method to expose a single substrate being processed to a plurality of original masks. As an alignment method, a global alignment method disclosed in Japanese Examined Patent Publication No. 7-120621 is used. In this alignment method, position measurement information of alignment marks in a plurality of sample shot areas on the substrate is processed using a statistical technique to calculate the position of each shot area.
The inventors of this invention have learned that the overall position accuracy of the substrate is greatly affected not only by the position accuracy of each shot area, but also by error components, such as magnification, rotation and skew at each shot area (hereinafter referred to as xe2x80x9cin-shot error componentsxe2x80x9d) as the accuracy level improves today. Non-linear deformation of the substrate and error introduced in film formation are considered to cause the in-shot error components.
Conventionally, the in-shot error components are not corrected, or, if corrected, the in-shot error components are treated as being a constant, regardless of the shot area position within the substrate.
It is a first object of the present invention to improve alignment accuracy by correcting an in-shot error component, which is an error component varying with a shot area position.
It is a second object of the present invention to provide a method that permits an in-shot error to be corrected, while performing alignment at a throughput at the same level as that achieved in the conventional method. In other words, the second object is to provide a method that works if at least one measurement is made in each of the X direction and the Y direction at each sample shot area, as in the conventional method.
To achieve the first object, an exposure apparatus of the present invention, in a first aspect, includes a detecting unit for detecting a position of a representative point within a representative area from among a plurality of areas in the substrate, to determine an in-area error in the representative area, a statistical calculation unit for statistically calculating the in-area error of each area in the substrate, based on the determined in-area errors of the representative areas, and a correcting unit for correcting the position of the substrate in accordance with the calculated in-area error, to successively process the areas of the substrate.
In a preferred embodiment, a plurality of representative points are set up in one representative area, the detecting unit includes a measuring unit for measuring the positional deviation in each of the plurality of representative points, and the in-area error of the representative area is determined based on the measured value of the positional deviation.
In a preferred embodiment, a plurality of representative areas are set up, and the statistical calculation unit determines the in-area error of each area in the substrate, based on the in-area error determined for each representative area.
In a preferred embodiment, at least three representative areas are set up in the substrate.
In a preferred embodiment, the in-area error includes at least one of a magnification component and a rotational component.
In a preferred embodiment, the exposure apparatus is of a step-and-repeat type, which stepwise moves a substrate stage holding the substrate thereon to set an area of the substrate to an exposure position before exposing the area of the substrate, and the correcting unit drives the substrate stage, an original mask stage holding the original mask thereon, or part of a projection lens unit during the stepwise movement to correct the in-area error of the area to be exposed.
In a preferred embodiment, the exposure apparatus is of a step-and-scan type, which stepwise moves a substrate stage holding the substrate thereon to set an area of the substrate to an exposure start position before exposing the substrate in a scanning exposure manner, and the correcting unit drives the substrate stage, an original mask stage holding the original mask thereon, or part of a projection lens unit during the stepwise movement or scanning exposure operation to correct the in-area error of the area to be exposed.
In a preferred embodiment, the in-area error includes a skew component.
In the first aspect of the present invention, an exposure method includes the steps of detecting a position of a representative point within a representative area from among a plurality of areas in the substrate, to determine an in-area error of the representative area, statistically calculating the in-area error of each area in the substrate, based on the measured in-area errors of the representative areas, and correcting the position of the substrate in accordance with the calculated in-area error, to successively process the areas of the substrate.
In the first aspect of the present invention, a device manufacturing method includes the steps of detecting a position of a representative point within a representative area from among a plurality of areas in the substrate, to determine an in-area error of the representative area, statistically calculating the in-area error of each area in the substrate, based on the determined in-area errors of the representative areas, and correcting the position of the substrate in accordance with the calculated in-area error, to successively process the areas of the substrate.
To achieve the second object, an exposure apparatus of the present invention, in a second aspect, includes a detecting unit for detecting a position of a representative point within a representative area in the substrate, a determining unit for determining the positional deviation of each of a plurality of the representative areas from among a plurality of areas in the substrate, based on the detection by the detection unit, a statistical calculation unit for statistically calculating the positional deviation of each area in the substrate, based on the determined positional deviations of the representative areas, a calculating unit for calculating an in-area error in each area, based on the statistically calculated positional deviation of each area, and a correcting unit for correcting the position of the substrate in accordance with the calculated in-area error, to successively process the areas of the substrate.
In a preferred embodiment, the statistical calculation unit calculates the positional deviation of each area in the substrate by employing an approximation equation of a second or higher degree.
In a preferred embodiment, the calculating unit calculates the in-area error, based on a rate of change in the positional deviation of each area.
In a preferred embodiment, the in-area error includes at least one of a magnification component and a rotational component.
In a preferred embodiment, the exposure apparatus is of a step-and-repeat type, which stepwise moves a substrate stage holding the substrate thereon to set an area of the substrate to an exposure position before exposing the area of the substrate, and the correcting unit drives the substrate stage, an original mask stage holding the original mask thereon, or part of a projection lens unit during the stepwise movement to correct the in-area error of the area to be exposed.
In a preferred embodiment, the exposure apparatus is of a step-and-scan type, which stepwise moves a substrate stage holding the substrate thereon to set an area of the substrate to an exposure start position before exposing the substrate in a scanning exposure manner, and the correcting unit drives the substrate stage, an original mask stage holding the original mask thereon, or part of a projection lens unit during the stepwise movement or scanning exposure operation, to correct the in-area error of the area to be exposed.
In a preferred embodiment, the in-area error includes a skew component.
In the second aspect of the present invention, an exposure method includes the steps of detecting a position of a representative point within a representative area in the substrate, determining the positional deviation of each of a plurality of the representative areas from among a plurality of areas in the substrate, based on the detection in the detecting step, statistically calculating the positional deviation of each area in the substrate, based on the determined positional deviations of the representative areas, calculating an in-area error in each area, based on the statistically calculated positional deviation of each area, and correcting the position of the substrate in accordance with the in-area error, to successively process the areas of the substrate.
In a preferred embodiment, the step of statistically calculating the positional deviation calculates the positional deviation of each area in the substrate employing an approximation equation of a second or higher degree.
In the second aspect of the present invention, a device manufacturing method includes the steps of detecting a position of a representative point within a representative area in the substrate, determining the positional deviation of each of a plurality of the representative areas from among a plurality of areas in the substrate, based on the detection in the detecting step, statistically calculating the positional deviation of each area in the substrate, based on the determined positional deviations of the representative areas, calculating an in-area error in each area, based on the statistically calculated positional deviation of each area, and correcting the position of the substrate in accordance with the in-area error, to successively process the areas of the substrate.